Assessment of Phenolic and Indolic Compounds Removal from Aqueous Media Using Lignocellulose-Derived Surface-Modified Nanoporous Carbon Adsorbents: A Comparative Study

Jandosov J. Chenchik D. Baimenov A. Silvestre-Albero J. Bernardo M. Azat S. Doszhanov Y. Sabitov A. Busquets R. Howell C. Mikhalovsky S. Mansurov Z.
January 2026 Multidisciplinary Digital Publishing Institute (MDPI)

International Journal of Molecular Sciences
2026 #27 Issue 2

P-cresol, indole and indole-3-acetic acid (IAA) are catabolites of amino acids, formed by the gut microbiome. Most of these aromatic hydrocarbon derivatives are excreted by the colon before reentering the body to form “exogenous” protein-bound uremic toxins (PBUTs), which aggravate chronic kidney disease (CKD). Removal efficiencies of these PBUT precursors from model phosphate-buffered saline solutions by three different surface-modified nanoporous carbon adsorbents (PCs) were studied. PCs were produced by physicochemical and/or acid base activation of carbonized rice husk waste. Removal rates achieved values of 32–96% within a 3 h contact time. High micro/mesoporosity and surface chemistry of the N- and P-doped biochars were established by N₂ adsorption studies, SEM/EDS analysis, XPS and FT-IR-spectroscopy. The ammoxidized PC-N1 had the highest adsorption capacity (1.97 mmol/g for IAA, 2.43 mmol/g for p-cresol and 2.42 mmol/g for indole), followed by “urea-nitrified” PC-N2, whilst the phosphorylated PC-P demonstrated the lowest adsorption capacity for these solutes. These results do not correlate with the total pore volume values for PC-N2 (0.91 cm³/g) < PC-P (1.56 cm³/g) < PC-N1 (1.84 cm³/g), suggesting that other parameters such as the micropore volume (PC-N1 > PC-N2 > PC-P) and the interaction of surface chemical functional groups with the solutes play key roles in the adsorption mechanism. N-doped PC-N1 and PC-N2 have basic functional groups with higher affinity with acidic IAA and p-cresol. The ion-exchange mechanism of phenolic and indolic compound chemisorption by nanoporous carbon adsorbents, modified with surface N- and P-containing functional groups, has been proposed.

adsorption mechanism , nanoporous carbon adsorbents , physicochemical activation , uremic toxin precursors

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Institute of Combustion Problems, 172, Bogenbay Batyr St., Almaty, 050000, Kazakhstan
Faculty of Chemistry and Chemical Technology, Al-Farabi Kazakh National University, 71, Al-Farabi Avenue, Almaty, 050012, Kazakhstan
Laboratory of Engineering Profile, Satbayev University, 122/22, Baitursynov St., Almaty, 050012, Kazakhstan
Laboratory of EPR spectroscopy, Institute of Physics and Technology, 11, Ibragimov St., Almaty, 050000, Kazakhstan
Laboratorio de Materiales Avanzados, Departamento de Química Inorgánica, Universidad de Alicante, Alicante, 03690, Spain
Departamento de Química (DQ), Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa (UNL), Caparica, 2829-516, Portugal
School of Life Sciences, Pharmacy and Chemistry, Kingston University, Penrhyn Road, Kingston upon Thames, KT1 2EE, United Kingdom
Enteromed Ltd., 85 Great Portland St., London, W1W 7LT, United Kingdom
ANAMAD Ltd., Sussex Innovation Centre, Science Park Square, Falmer, Brighton, BN1 9SB, United Kingdom
Chuiko Institute of Surface Chemistry, 17, General Naumov St., Kyiv, 03164, Ukraine

Institute of Combustion Problems
Faculty of Chemistry and Chemical Technology
Laboratory of Engineering Profile
Laboratory of EPR spectroscopy
Laboratorio de Materiales Avanzados
Departamento de Química (DQ)
School of Life Sciences
Enteromed Ltd.
ANAMAD Ltd.
Chuiko Institute of Surface Chemistry

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